1. Field of the Invention
This invention relates to the field of orthopedic surgery, and to the field of implantable bone lengthening devices.
2. Description of the Related Art
The typical apparatus used for bone lengthening consists of a special nail implanted in a cavity formed by the removal of the bone marrow from, for example, a leg bone. With the nail in place, an external longitudinally-adjustable frame assembly is secured to the ends of the bone. One end of the frame is pinned to an end of the bone and the other end of the frame is pinned to the other end of the bone having the nail located therein. The bone is then broken and this adjustable frame is periodically lengthened causing the bone, as the break is knitting, to also lengthen. This external frame fixation system is difficult to securely locate on the patient, resulting in discomfort and an unattractive appearance. More seriously, the pins, being secured in the bone and protruding outside of the skin, increase the risk of infection.
Thus, there is a need for a bone lengthening device which incorporates an extension mechanism into the structure of the implantable nail body, thereby eliminating the need for this external frame and all of its related problems.